Switch apparatus



1954 w. M. ALTHERR SWITCH APPARATUS 3 Sheets-Sheet 1 Filed April 16,1951 xxx 1 E M m w MA Mmw .I ww

Dec. 14, 1954 3 Sheets-Sheet 2 Filed April 16, 1951 Dec. 14, 1954 w. M.ALTHERR SWITCH APPARATUS 3 Shets-Sheet 3 Filed April 16, 1951 UnitedStates Patent Office 2,697,150 Patented Dec. 14, 1954 SWITCH APPARATUSWalter M. Altherr, St. Louis, Mo., assignor, by mesne assignments, to A.B. Chance Company, Centralia, Mo., a corporation of Missouri ApplicationApril 16, 1951, Serial No. 221,229

8 Claims. (Cl. 200-113) This invention relates to switch apparatus, andwith regard to certain more specific features, to thermostatic switchingmeans for controlling multiple street-lamp lighting circuits or thelike. The invention is an unprovement upon the construction shown, forexample, in United States Patent 2,444,745, dated July 6 1948.

Among the several objects of the invention may be noted the provision oflow-cost, switch apparatus which, without making certain lamp operationssimultaneous, reduces the time interval required for a sequence of suchoperations in response to a control operation; the provision ofapparatus of the class described wh1ch, as between cold and warm ambienttemperature operat ng conditions, makes said intervals more nearly equalw thout requiring special ambient temperature compensat ng means; theprovision of apparatus of th1s class which has no critical operatingconditions and wh ch therefore may be more simply, quickly and reliablyad usted, either at the factory or in the field; the provision ofapparatus of the class described which is less subject to breakdownunder normal operating conditions and under abnormal overload conditionssuch as from lightning surge s or the like, requiring no overload fuses;and the prov sion of apparatus of this class which requires only asingle pilot line for application to any of a wide variety of circuits.Other objects will be in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exempllfied 1n the structures hereinafter described, and the scope ofwhich will be indicated in the following claims.

In the accompanying drawings, in which several of various possibleembodiments of the invention are illustrated Fig: l is a circuit diagramillustrating one application of one embodiment of the invention;

Fig. 2 is a circuit diagram illustrating an application of a secondembodiment of the invention;

Fig. 3 is a circuit diagram illustrating another application of theinvention;

Fig. 4 is a front elevation of one form of switch made according to theinvention;

Fig. 5 is a cross section taken on line 5-5 of Fig. 4;

Fig. 6 is a cross section taken on line 66 of Fig. 4, being also a crosssection on line 66 of Fig. 9;

Fig. 7 is a horizontal section taken on line 77 of Pi 4' FigfS is across section taken on line 88 of Fig. 7;

Fig. 9 is a view similar to that of Fig. 4 but showing another form ofswitch made according to the invention;

Fig. 10 is a right-end view of both switch forms shown in Figs. 4 and 9,these forms being identical except for parts that do not show in Fig.10, the dotted lines illustrating a cover which may be employed;

Figs. 11, 12 and 13 are fragmentary views similar to portions of Fig. 10but illustrating an operative sequence starting with the Fig. 10position of parts;

Figs. 14l6 are diagrammatic views of certain cam and contact parts shownon Figs. 5 and 6, and illustrating an operating sequence starting withthe positions of parts shown in said Figs. 5 and 6; and,

Fig. 17 is a fragmentary view of certain contacts, showing analternative construction.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

In said Patent 2,444,745 is shown improved circuitcontrol apparatusemploying in general a single pilot line which controls thermostaticswitches for operating lamps of street-lighting circuits. The advantageof thermostatic switches for the purpose has been that when the pilotline is energized the thermostatic switches inherently have suliicientdifferences in operating characteristics to prevent all of the controlof lamps from being thrown onto the power line substantially at once, asis the case with magnetically operated switches. But such a systemrequires relatively long intervals between the time that a first lampturns on or off and the time that a last lamp turns on or off. This maybe as much as 15 minutes under not unusual operating conditions. Despitecompensation, this interval has been variable between extremes ofambient temperature conditions, and under certain circumstancesadjustment of the device has been critical. Also, in certain peculiar(although not all) circuit applications, more than one pilot line hasbeen required. By means of the present invention the stated advantagesof this prior system are retained, with additional ones relating to theabove matters.

A street-lighting circuit is used in the present description as anexample of a type of circuit which may be controlled by the presentinvention, the advantages of the invention being particularly desirablein such circuits, but this application is not to be taken as limiting.

Referring now more particularly to Figs. l3 there is shown at P a v.single-phase portion of an ordinary l20240 v. three-wire powerdistribution circuit. Connected to a lead 1 of this circuit is a pilotline 3 in which is an on-off control switch C which may be of anysuitable type, operated, for example, either manually or by means of aknown type of time clock. Pilot line 3 connects in series certainthermostatic elements 35 of operating switch units hereinafter to bedescribed and the assemblies of which are generally indicated by thedotted lines 0 in Figs. 1-3. The pilot line 3 is connected to the otherside 7 of circuit P through a series resistance 9. At numerals 11 and 13are typical light bulbs connectible in individual groups across thecircuit P by operation of the switch assemblies 0. The number of lampsin a group is optional and may be one or more, two being shown. Eachgroup is usually localized in position, as on a single or several polesat some location along a street. Their connections to side 7 of circuitP are shown at 15. Their other connections to the lead 1 of circuit Pare shown at 17. These connections are made through suitablecam-operated contact banks S or D within the switch assemblies 0. Theparticular connections in respect to the contact banks S or D dependupon which of several types of switches are to be used at 0 (describedbelow), and the manner in which the switches are arranged. But in anyevent, only one pilot line 3 is needed in any of the variousapplications of operating switch assemblies 0, as illustrated, forexample, in Figs. 1, 2 and 3. Thus it will be clear that the system isadaptable to a wide variety of applications without multiplying pilotlines such as 3. Certain four-lobed cams for operating the contact bankS are shown at 4. These are operated from thermostats generally indexedT and which will be described in detail below. Certain two-lobed camsfor operating the contact bank D are shown at 2 Figs. 2 and 3). Theseare also operated from the thermostats T. At F are shown generallycertain safety switch components of the thermostats T for preventingtheir burn-out under certain operating conditions to be described.

Before giving an operating description of Figs. 1-3, details will bedescribed of the structures and functions of switches such as showngenerally at 0. Referring first to Figs. 48 and 10, a form of the switchsuch as used at 0 will be described, which incorporates both contactbanks S and D and both types of cams 4 and 2, respectively (as appliedin Fig. 2). Referring to said Figs. 48 and 10, numeral 19 illustrates aninsulating base on which is supported a generally U-shaped conductiveframe 21 having legs 23 and 25 and an upper arm 55. Extending from theleg 23 (Fig. 7) is a conductive hollow threaded stud 27 which is axiallyslotted as shown at 29. This stud accepts a pintle 31 which forms abearing support between the legs 23 and 25.

.shaft collar.

3 This pintle is flattened out as at 33 to key into the slot 29. Aroundthe stud 27 is located a spiral bimetallic conductive thermostaticelement 35 which has a central tongue 37 keyed into the slot 29. Thisthermostatic element 35 is flanked by two porcelain enameled protectivewashers 39 which have both heat-resisting 'and insulating properties. Alock nut 41, threaded to the stud 27, serves to clamp the central partof element,35 between ofiset central portions 36 of the washers. Theresulting reactions hold the stud 27 in place. its angular position maybe adjusted by loosening the lock nut 41, and turning 27 by means of ascrew driver in slot 29 and then again tightening the lock nut. Thisadjusts the angular position of the center of the thermostatic element35 and hence its operating characteristics, as will appear. Tongue 37 inslot 219 axially positions the I pintle 31, as shown in Fig. 8. Thus thethermostatic element 35 is centrally anchored and in conductive relationto the frame 2i. A terminal for the frame is provided at 96.

Around the pintle 31 is located a sleeve 43. This sleeve is locatedwithin a circular hole in a rotary cam- 45 which is in the form of apolygonal bushing. The camshaft 45 carries in keyed relation (by reasonof its polygonal form; Figs. and 6) an eight-toothed ratchet 47, aninsulating spacer 49, an insulating washer 51, the four-lobed cam 4 andthe two-lobed cam 2. The ends of the camshaft 45 are upset, as shown, to

hold together as a unitary rotary assembly the parts.

2, 4 and 47. Cams 2 and 4 are composed of insulating material; ratchet47 is not, although it might be.

Wound around the spacer 49 is a helical spring 53 which has one endanchored in the extension 55 from the leg 25, as indicated at 57 in'Fig.4. The other end of this spring is formed as a bail 59 having, a leg 61and a leg 63. The inner end of leg 63 forms a loose wrap 65 around agroove 67 in the nut 41. Thus the spring at one end is anchored at57 butthe wrap 65 at the other end is rotary in the groove 67.

The bail 59 constitutes apawl drive for the ratchet 4 7, spring 53biasing it in forward ratchet-driving directron.

The thermostatic element 35, except at its anchored central portion, isfree andspirals to its outer end 69. where it is provided with aninsulating collar 71 engageable with the bail 59. When the thermostaticelement 35 cools, it tends to unwind counterclockwise (Fig. thus forcingthe bail '59 toward a stop 73 which forms an extension from the leg 23.This increases the tension in the spring 53, which has been prewoundprior to anchoring at 57, so as to bias its bail clockwise (Fig. 10).When the thermostatic'element 35 heats, it tends to wind clockwise andthe tensioned spring 53 follows it, as illustrated in Fig. 11, tainpoint, the leg 61 of the bail 59 is caughtbehind one of the laterallydirected teeth 75 of, the ratchet 47. At this time the ratchet isprevented from moving clockwise because of engagement by another one ofits teeth 75 with a spring pawl 77. This spring pawl is'anchored at itslower end, as shown at 79, to an insulating block 81 The pawl 77 biasescounterclockwise, the motion being limited by engagement of its upperend.83 witha second stop 85 extending from the leg '23. This stop is forthe purpose of allowing only enough counterclockwise movement of pawl 77to latch under'a tooth 75 without acting as a friction brake on'theratchet 47. Upon continued heating of the thermostatic element 35 itmoves from the Fig. 11 to the Fig. 12 position, leaving behind the bail59, which then applies the tension of spring 53 to ratchet 47, but theratchet is 'held against clockwise movement by the pawl 77. Afteraperiod of further heating the insulating collar 71 engages an 'offsetend portion 84 ofthe pawl'77. This disengages the pawl 77 from theratchet 47, and the bai spring 53 advances the ratchet one-eighth turnwith a snap action (compare Figs. Hand 13), the leg 61 'of the bailacting asa drivingpawl. The movement'of bail 59 is limited by itsengagement with the stop. 85

to limit rotation of the ratchet'to one-eighth of a'turn.

When the spring 53 snaps, stop 85'prevents bail59 from striking theinsulating collar 71 to avoid'damage to the Pawl 87 is anchored at 88 toan insulating block 96. The pawl 87 also prevents reverse movement ofthe ratchet 47, whenthe thermostaticfelement 35' cools v sufficiently tomove itcounterclockwise from the Fig. 12

After following to a cer- 1 s9 ofthe,

through the Fig. 11 to the Fig. 10 initial position. During thiscounterclockwise movementthe collar 71 reengages the bail 59 and thespring 53 is rewound. During clockwise heating movement of thethermostatic element 35 it is at first aided by the unwinding action ofthe spring-mounted bail 59 (Fig. 11) and thereafter may freely movewithout resistance until it releases the pawl 77. Therefore, its heatingmovement toward its tripping position for pawl 77 is relativelyunimpeded, which means that this action may take place rapidly andreliably. The thermostatic element '35 is provided at its 8 isfoperatedby the four-iobed cam 4, and the contact bank D is operated by thetwo-lobed cam 2. Thedetails of each bard; S and.D are the same, and thedescription of one will serve for both (Figs. 4, 5 and 6) and the samereference numerals will be used for each Each contact bank S and D hasmounting spring fingers 9 1, 93 and 95, insulated-from each other andfrom the-frame by blocks of insulation 97. Outer-fingers 9; and 9 5 areconductively connected as indicated at 919 for. connection with thelines 17 (see also Figs. 1-3). The middle finger 93 ofv each bankcarries a terminal 101 for connection with the lamps 11; and 13. Aterminal, 1tl2-is; provided, for each of fingers 91 and 95, eachincluding an insulated bolt connection 16 4} in conductive relation toa. finger- 91, and hence (in view of connector 99) in condi c tiverelation with bothfingers91 21111195. Bolts 194 are not in conductiverelation with fingers '93 (see insulating sleeve94), Note thatconnections 17 attach-toterminals LQZKEigs. L3). The wires leading fromterminals 101 and if lpass through suitable. openings in the base 19.

These wires are shown diagrammatically in Figs. 1 3 but not in Figs.4-l0 so. asnot to confuse the latter. Behind each finger is a pressurespring follower finger 103 for following engagement with therespectivecam 2 or 4 for operating the. spring fingers 91, 93 and 95 toclosing and opening positions,

Contacts 107 on the fingers 93 and 95 are preferably composed'of atungsten-silver alloy or the like, which has a high melting pointpreventing them from weld- .ing together. duringoperation. :Atter 'oneortwo opera- 'shuntcontacts which close only. afterclosureof thecircuit bycontacts 197 and open before opening of contactsg107. Thus, they nevercarry an open-circuit voltage drop. Moreover, they provide a lowresistance shuntaround high-resistance contacts 107' when the latter areclosed.

As above implied, during closing action of; the contacts1(E7-close'first, and then contacts 165-. Thus high resistance contacts107' protect contacts against initial inrus'h'of-curr'ent intothe coldlamps. After the lamps heat up and increase their resistancethe-subsecircuit,

" quent lower current is carried by the shunt contacts 105 with lowerresistance. 5 Upon opening action, contacts 1G5 firstseparate withoutvoltage. across them and man contacts 197 open. Any. are that tends tobe formed will'be handled by contacts 107. Since these-areof thehigh-melting variety, they do not melt but maintain the desiredhigh-resistance burned-or oxidized condition, useful on thenext closingaction. Inorderto. protect contacts 105 against voltages. as. fromlightning surges or the ;like, the end of spring strip 93. is bent'toward and over the end of strip 91 to provide a small surge gap 109.

Figs. 5, 6 and 14-16 dicgrammatically illustrate the sequence of actionof the cams 4 and 2 in connection with their respective contact banks Sand D. Each heating pulse of the thermostatic element 35 results in aone-eighth turn of the camshaft 45. In the case of the four-lobed cam 4,this will cause successive closings and openings of the contact bank S,according to successive 45 movements of the cam 4, assuming an openposition at the start. in the case of the two-lobed cam 2, a first 45movement causes a first closing of contact bank D (compare Figs. 5 and14). For the next two 45 movements cam 2 holds this bank D closed(compare Figs. 1446). In the meantime, bank S has alternately closed,opened and reclosed. The following table will make the above clear. Theleft-hand column in this table indicates the successive 45 angularpositions of the cams 2 and 4 covering a two-day operating period. Thesecond column shows the condition of contact bank D and the third columnthe condition of contact bank S. It will be understood that the 45?rotations of the cams are accomplished by closing of the control switchC at suitable time intervals, as shown by way of example in theright-hand column.

In some applications of the invention the double-lobed cam 2 andassociated contact bank D are not required. In such event the contactbank D may be left out of the final wired circuit, which is one reasonfor the use of two terminals 101 such as shown in Fig. 4. Or the form ofthe switch shown in Fig. 9 may be used in which cam 2 and the parts ofcontact bank D operated thereby are eliminated. In this case most of theremaining parts are identical to those already described, andcorresponding reference numerals are therefore applied to correspondingparts which show in Fig. 9. Exceptions are that the U- shaped frame 21is narrower. It therefore has been renumbered 121. Its legs arerenumbered 123 and 125, the extension 55 being renumbered as 155. Theshorter pintlc is renumbered 131. Otherwise the device of Fig. 9 is thesame as that shown in Figs. 48. It will be under stood that Fig. 10 is acorrect right-end view of both Figs. 4 and 9. In Fig. 10 is shown indotted lines a cover 111, which may be used for outdoor mounting of theswitches on poles. A similar cover may be used on the Fig. 4 form of theswitch.

In Fig. l is shown one application of the invention, in which there isused in each operating switch assembly 0 a switch of the type shown inFig. 9, having only one four-lobed cam 4 operating one contact bank S.These switches are wired with their thermostatic elements 35 in seriesin the pilot line 3. Each contact bank S under control of a cam 4controls lamps 15, 17 connected in parallel across the circuit P. Itwill be understood that there is one switch assembly 0 and one group oflamps 11, 13 on, say, each of a number of poles supporting thewire-forming circuit P and the wire-forming pilot line 3. The exactnumber of lamps used at 11 and 13 is immaterial and this may be reducedto one or increased to any other number on a given pole within limits.Assume that all of the lamps 11, 13 are to be lighted, say at 6:00 p. m.The control switch C may be operated manually or by a time clock for asuitable interval long enough to assure that all of the thermostaticelements 35 become operative, As soon as the control switch C is closed,a pulse of current flows in series through all of the thermostaticelements 35 in the pilot line 3 and through the resistance 9. Eachthermostatic element 35 has a low resistance, for example, .11 ohm. Theconductors of line 3 and resistance 9 are adapted to add a properresistance to draw a substantial current at volts. Since this additionalresistance is relatively high, it makes little difference in the voltagedrop across the pilot line whether or not the thermostats are in orshunted out of this circuit. Thus when switch C is closed, an initialpulse of current passes through all of the thermostatic elements 35. Thecurrent through each thermostatic element F flows through 94, 92, 89,35, 121, 96. The arrangement is such that within about 1 /2 minutes orless, each of the thermostatic elements 35 has moved to trip its pawl 77with consequent movements of the respective cam 4 through a 45 interval,thus closing the respective contact bank S. This connects all lamps 11and 13 across the circuit P. Unlike magnetic relays, the thermostaticswitches have slight variations in their operating characteristics, andhence do not connect all of the lamps across the line at once. Thestated time interval of 1 /2 minutes or less, is much iess than the timeinterval required by former constructions such as in said Patent2,444,745, because the thermostatic elements 35 are quickly heated to ahigh temperature by heavy current flow through them, instead of beingindirectly heated by auxiliary heaters. Thus the operatingcharacteristics of the elements 35 are fast and less critically affectedby ambient temperature conditions, even without compensation for suchconditions. The heating temperatures for operation of the thermostaticelements 35 are, for example, several hundred degrees and entirely outof the range of ambient temperature conditions even on the hottest day.The arrangement is in fact such that if the inrush of current werepermitted to continue through these elements 35, they would become redhot and might eventually burn out. This contingency is prevented byreason of the fact that after tripping action of a given switch assembly0 has occurred so as to light its lamps 11, 13, continued flow ofcurrent causes the respective thermostatic element 35 to move itsconductive arm 89 against the stop 85 of frame 21 (compare Figs. 12 and13). Thus members 89 and 85 constitute the short-circuiting switch Findexed on Fig. l, which shunts the current around the respectivethermostatic element 35. Element 35 then proceeds immediately to cooland move from the Fig. 13 to the Fig. 12 position, whereupon the switchF reopens and the current again flows through the thermostatic element35. Thus a short-throw repetitive opening and closing action of switch Fcontinues as long as the control switch C is closed. This prevents thethermostatic element 35 from overheating and burning out but in view ofits low resist ance (.11 ohm) does not substantially change the currentin the pilot circuit. This short-throw shunting action does not affectany movement of the respective cam 4 because it is not suificient tomove back the bail 59 to pick up another 45 movement of the ratchet 47.During the pulsing interval, other switches 0 will be tripping shut andacting likewise. Finally, after the interval of time required fortripping all switches O shut (1 /2 minutes or so), the control switch Copens (time clock) or is opened (manual operation), whereupon all of thether mostatic elements 35 completely cool. At about l60 F. eachthermostatic element 35 has returned to the position shown in Fig. 10,so as to cause its spring 53 to be rewound and to drop behind a nextsucceeding tooth 75 of ratchet 47. It requires about 7 minutes for thereturn action, but the delay here involved is of no disadvantage.

In order to turn of the lights, say at 6:00 a. m., the control switch Cis again closed for the requisite time (l /z minutes or so), whereuponthe cycle repeats itself, except that in this case each contact bank Sreopens.

By way of example, the total resistance in pilot line 3, including theresistance 9, may be about 4 to 9 ohms, which will provide a largecurrent of about 30 to 13 amperes, a proper range of current forreliably and quickly operatively pulsing all of the switch units 0within 1 /2 minutes. If the system is expected to operate in lowerambient temperatures to maintain the 1 /2 minute operating interval,more pulse current may be used by decreasing the resistance 9. But inany event, the pulsing time for operation is not widely different forlarge ranges in ambient temperature conditions because of the lowresistances of the thermostatic elements 35 with the high currents drawntherein and the resulting high temperature aoperations thereof, whichoperations are fairly constant and independent of said ambienttemperature operating conditions. Thus the switch is very reliable inoperation,

the large current passed through the thermostaticelemerits 35 assuringreliable and quick movements thereof in the cam-driving directions. Itmay be remarked that even though adjacent coils of the thermostaticelements .35 might touch, so asto shunt out some of the length :ofthetherrnostat, still thereliability and fast action of .at, say, l2t00in. (when the traflic becomes less), to turn off some of the lamps,leaving the remainder on; then for the morning trafiic rush, to turn allthe lamps on for an interval starting, say, at :00 a. m.; and finally toturn them all off, say, at 7:00 a. m. The above-mentioned tableindicates such requirements, and Fig. 2 indicates how the double-camswitch is used in units 0 in the pilot line 3 to meet theserequirements. In this case, switch contact bank S controls'lamp l1 andswitch contact bank D controls lamp 13, since as shown in Fig. 2 theseswitches are in the respective parallel lamp connections. Comparison ofFig. 2 with the table, and what has been said above, will make clear theFig. 2 operation. Obviously each unit 0 operates once per pulse ofcurrent when control switch C closes. In each unit, both cams 2 and 4operate at once in response to tripping from the respective thermostaticelement 35. The sequential operation shown in the table is due to thecam shapes.

It will be understood that in the case of a single-cam switch such asshown in Fig. 9, the two-lobed cam 2 may be substituted for thefour-lobed cam 4. Then the wiring shown in Fig. 3 may be employed,alternate groups of lamps 11 and 13 on a line of poles being controlledby alternate units 0 having four-lobed cams 4 and two-lobed cams 2,respectively. The operation will be similar to that in Fig. 2, exceptthat inFig. 2 certain pairs of cams 2 and 4 trip simultaneously, whereasin Fig. 3 corresponding pairs of cams 2 and 4 operate only approximatelysimultaneously. This is because in Fig. 3 each cam 2 w or 4 is operatedby a separate thermostatic element 35, whereas in Fig. 2 certain pairsof such cams are operated by a single thermostatic element 35. Thediiference lies in the fact that in Fig. 3 on a given pole there is aswitch assembly 0 incorporating either a cam 4 or a cam 2. Thus all ofthe lamps on a given pole are either off or on. Hence when some of thelights are oli (as distinguished from all of them being on or oil) thelamps on certain alternate poles are all on and the lamps on alternatepoles are all off. in the case of Fig. 2, all of the lamps on all polesare on or oif: or some of the lamps on all poles are on and some off.Thus in the case of Fig. 2, when some of the lamps are off, thebrightness of the light from all poles is reduced, whereas in the caseof Fig. 3, the brightness of the light from alternate poles is maximumand that from the other alternate poles is zero.

It will be understood. that other variations in the switch structuresand their applications are possible. For example, in some cities a powercircuit such as P is strut: along one set of poles on one side of thestreet and along another set of poles on the other side of the street.Obviously, it would be possible to use units 0 with fourlobed cams 4 onone side of the street, and units 0- with two-lobed cams 2 on the otherside of the street, with a single pilot line 3 connecting them all inseries, operated by one control switch C. Such a system would operatesubstantially as above describedin connection with Fig. 3, except thatduring partial lighting periods all of the lamps on one side of thestreet would be out; otherwise, they would all be on or oii.

In Fig. 17 is shown an alternative mounting for the contact banks S andD, wherein like numerals designate like parts. In this alternative formthere is mounted behind each contact spring )1 a resilient stop bar 202which limits the clockwise movement of the member 91 upon opening of theswitch contacts 1%. There is also mounted in front of the centralcontact spring 93 another resilient stop bar 203 which rapidly damps anyvibratory motion that 93 may have imparted to it upon contact opening.These elements further minimize arcing under large values of current. Itis to be understood that the resiliency of the stop bars 201 and 203 isprovided so that they permit closure of contacts 105.

It will be understood that although the invention is primarily adaptedto control of street-lighting circuits, it may have other applicationsto circuits wherein the load members are other than lamps. In such acase the contact banks or lamp switches S and D would constitute loadswitches.

From the above, the stated advantage of the invention will be clear, i.e.,

(l) The structural principles of the thermostatic switches are such thatmost of the parts are applicable to switches made either with two-lobedcams only, fourlobed cams only, or with both four-lobed and two-lobedcams. Thus production costs are minimized for a wide variety ofstreet-lighting applications.

(2) in the usual street-lighting applications of the invention, only asingle pilot wire is necessary, making control possible from a singlecontrol switch. This reduces installation costs.

(3) T he operating time for connecting or disconnecting all or some ofthe lamps is considerably reduced (without making it zero) and made moreindependent ofambient temperature conditions, without the necessity fortemperature-compensating elements in the switches.

(4) The switches are easy to adiust and reliable in operation underoverload conditions without the necessity for the use of protectivefuses.

Cross reference is here made to my copending divisional application,Serial Number 322,279, filed November 24, 1952, for Circuit ControlSystem.

in view of the above. it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention. it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. Thermostatic switch apparatus comprising a support, a switch carriedby the support, switch-operating mechanism carried by the support, drivemeans for said mechanism mounted on the support adapted for forwardmovement from a retracted position to drive said mechanism, and beingspring-biased in forward mechanismdriving direction, a stop for saidmechanism mounted on the support for movement between amechanismengaging position and a disengaging position freeing themechanism, a thermostatic element mounted on the support and having afree portion movable in one direction upon heating of the element and inreturn direction upon cooling of the element, said free portion normallyengaging the drive means and holding it in its retracted position, andbeing movable away from the drive means and toward engagement with thestop upon heating of the element for moving the stop to its disengagingposition, the stop holding said mechanism against movement by the drivemeans until said free portion engages the stop, whereby the drive means,under its spring bias, drives said mechanism and overtakes said treeportion, said free portion moving in returndirection upon cooling of theelement-to return the drive means to retracted position.

-2. Thermostatic switch apparatus made according to claim 1, whereinsaid thermostatic element is connected into an electric circuit adaptedto heat the element, and wherein the'apparatus includes a shunt switchadapted to be closed by the thermostatic element after its free portionhas moved said stop to its disengaging position to shunt the flow ofcurrent around the thermostatic element.

3. Thermostatic switch apparatus comprising asupport, a switch carriedby the support, a ratchet movable on the support, means driven by theratchet for opening and closing the switch, a pawl drive for the ratchetmovably mounted on the support and engageable with the ratchet, saiddrive being movable forward from a retracted position to drive theratchet, and being spring-biased to move in forward ratchet-drivingdirection, a releasable stop for the ratchet mounted on the support formovement between 21 ratchet-engaging position and a retracted positionfreeing the ratchet, a thermostatic element mounted on the support andhaving a tree portion movable in one direction upon heating of-theelementand in return direction upon cooling of the element, said freeportion normally engaging the drive and holding it in its retractedposition, and being movable away from the drive and toward engagementwith the stop upon heating of the element for moving the stop to itsretracted position, the stop holding the ratchet against movement by thedrive until said free portion engages the stop and moves it to itsretracted position, whereupon the drive, under said spring bias, drivesthe ratchet and overtakes said free portion, said free portion moving inreturn direction upon cooling of the element to return the drive toretracted position.

4. Thermostatic switch apparatus made according to claim 3, wherein saidthermostatic element is connected into an electroc circuit for heatingthe element, and wherein the apparatus has a shunt switch adapted to beclosed by the thermostatic element after its free portion has moved saidstop to its retracted position to shunt the flow of current around thethermostatic element.

5. Thermostatic switch apparatus comprising a support, a switch carriedby the support, a cam rotary on the support and adapted upon rotationsuccessively to open and close the switch, a ratchet rotary on thesupport connected with the cam for rotating the cam, a pawl drive forthe ratchet movably mounted on the support and engageable with theratchet, said drive being movable forward from a retracted position todrive the ratchet, and being spring-biased to move in forwardratchet-driving direction, a releasable stop for the ratchet mounted onthe support for movement between a ratchet-engaging po sition and aretracted position freeing the ratchet, a thermostatic element mountedon the support and having a free portion movable in one direction uponheating of the element and in return direction upon cooling of theelement, said free portion normally engaging the drive and holding it inits retracted position, and being movable away from the drive and towardengagement with the stop upon heating of the element for moving the stopto its retracted position, the stop holding the ratchet against movementby the drive until said free portion engages the stop and moves it toits retracted position, whereupon the drive, under said spring bias,drives the ratchet and overtakes said free portion, said free por tionmoving in return direction upon cooling of the element to return thedrive to retracted position.

6. Thermostatic switch apparatus made according to claim 5, wherein thefree portion of the thermostatic element is electrically attached to oneside of a circuit, the other end thereof being in electrical contactwith the support, the support being electrically connected to the otherside of said circuit, and contacts on said support and said free portionadapted to be engaged to shunt the thermostatic element upon apredetermined movement thereof after movement of said stop to retractedposition.

7. Thermostatic switch apparatus made according to claim 5, wherein saidthermostatic element is constituted by a spirally coiled bimetallicstrip.

8. Thermostatic switch apparatus comprising a support, a switch carriedby the support, a cam rotary on the support and adapted upon rotationsuccessively to open and close the switch, a ratchet rotary on thesupport connected with the cam for rotating the cam, a pawl drive rotaryon the support and engageable with the ratchet, said drive beingswingable forward from a retracted position to drive the ratchet, andbeing springbiased to swing in forward ratchet-driving direction, areleasable stop for the ratchet mounted on the support for movementbetween a ratchet-engaging position wherein it stops forward rotation ofthe ratchet by the pawl drive and a retracted position freeing theratchet for forward rotation, a holding pawl mounted on the support forholding the ratchet against rotation in reverse direction, a bimetallicconductive spiral thermostatic element anchored at its inner end to thesupport and having a rotary outer portion movable in one direction uponheating of the element and in return direction upon cooling of theelement, said element being adapted for connection in a circuit for flowof current therethrough to heat it, said outer portion normally engagingthe pawl drive and holding it in its retracted position, and beingmovable away from the drive and toward engagement with the stop uponheating of the element for moving the stop to its retracted position,the stop holding the ratchet against movement by the drive and therebyholding the drive in its retracted position until said outer portionengages the stop and moves it to its retracted position, whereupon thedrive, under said spring bias, drives the ratchet and overtakes saidouter portion, said outer portion moving in return direction uponcooling of the element and being adapted to engage and return the driveto its retracted position, a shunt contact on said outer portion of theelement, and a shunt contact on the support engageable by said shuntcontact on said outer portion upon continued movement of said outerportion after the stop has been moved to its retracted position inresponse to continued heating of said element, the shunt contact on thesupport being electrically connected to the inner end of the element forshunting the element upon engagement of the contacts.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,535,360 Vickery Apr. 28, 1925 2,125,765 Butler Aug. 2, 19382,444,745 Mosley July 6, 1948 2,505,689 Richmeyer Apr. 25, 19502,549,532 Seaman Apr. 17, 1951

